21523380 has 24 divisors (see below), whose sum is σ = 60265632. Its totient is φ = 5739552.

The previous prime is 21523361. The next prime is 21523387. The reversal of 21523380 is 8332512.

It is a plaindrome in base 9.

It is a zygodrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 21523380.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523387) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 179302 + ... + 179421.

It is an arithmetic number, because the mean of its divisors is an integer number (2511068).

Almost surely, 2^21523380 is an apocalyptic number.

21523380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21523380 is an abundant number, since it is smaller than the sum of its proper divisors (38742252).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21523380 is a wasteful number, since it uses less digits than its factorization.

21523380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 358735 (or 358733 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21523380 is about 4639.3296929621. The cubic root of 21523380 is about 278.1656449457.

Adding to 21523380 its reverse (8332512), we get a palindrome (29855892).

The spelling of 21523380 in words is "twenty-one million, five hundred twenty-three thousand, three hundred eighty".